body {
    /* 流式布局屏幕宽度设置为100% */
    width: 100%;
    /* 最小宽度不小于320px，到这个尺寸后就不再缩放 */
    min-width: 320px;
    /* 最大宽度不大于640px */
    max-width: 640px;
    /* 页面居中显示 */
    margin: 0 15px;
    /* 字体大小 */
    font-size: 14px;
    /* 字体：如果是苹果手机就用第一个字体，如果不是用后面的字体 */
    font-family: -apple-system,Helvetica,sans-serif;
    /* 字体颜色 */
    color: #666;
    /* 行高设置为1.5 */
    line-height: 1.5;
}
ul {
    margin: 0;
    padding: 0;
    list-style: none;
}
/* 设置上面这个盒子的高度是45px，宽度不用管因为是流式布局 */
.app {
    padding-top: 30px;
    height: 85px;
}
.app ul li {
    float: left;
    height: 85px;
    background-color: #fff;
}
/* 设置3个盒子的百分比，3个盒子加起来是100 */
.app ul li:nth-child(1) {
    width: 20%;
}
/* 设置图片的尺寸为盒子的尺寸 */
.app ul li:nth-child(1) img {
    width: 85px;
}
.app ul li:nth-child(2) {
    width: 60%;
    font-size: 20px;
    line-height: 25px;
    padding-top: 15px;
    background-color: rgba(255, 255, 255, 0);
}
.app ul li:nth-child(3) {
    width: 20%;
}
.app ul li:nth-child(3) img {
    width: 85px;
    float: right;
    border-radius: 15px;
}
/* 焦点图 */
.Focus-picture img{
    border-radius: 20px;
    width: 100%;
}
/* 搜索 */
.search {
    position: relative;
    box-sizing: border-box;
    /* 这里搜索盒子给高度，不给宽度，这样可以实现左右缩放效果 */
    height: 65px;
    background-color: #eff2f9;
    margin: 20px 0 0 0; 
    border-radius: 20px;
    text-align: center;
    font-size: 16px;
    padding-top: 5px;
}
.search img {
    position: absolute;
    width: 30px;
    left: 250px;
    top: 15px;
}
.search p {
    position: absolute;
    display: inline-block;
    top: 5px;
    left: 300px;
}
/* 课程选择标题 */
.Courseselection {
    position: relative;
    padding-top: 25px;
    padding-bottom: 30px;
}
.Courseselection p:nth-child(1){
    font-size: 35px;
    font-weight: 700;
    color: black;
}
.Courseselection p:nth-child(2){
    position: absolute;
    top: 130px;
}
/* 课程选择目录 */
/* 机械基础 */
.machinery-foundation {
    position: relative;
    padding-top: 75px;
}
.machinery-foundation ul li:nth-child(2) {
    position: absolute;
    left: 120px;
    top: 75px;
}
.machinery-foundation ul li:nth-child(2) p:nth-child(1) {
    font-size: 19px;
    font-weight: 700;
    color: black;
}
.machinery-foundation ul li:nth-child(2) p:nth-child(2) {
    position: absolute;
    font-size: 14px;
    top: 39px;
}
/* 极限配合 */
.technical {
    position: relative;
    padding-top: 35px;
}
.technical ul li:nth-child(2) {
    position: absolute;
    top: 35px;
    left: 120px;
}
.technical ul li:nth-child(2) p:nth-child(1) {
    font-size: 19px;
    font-weight: 700;
    color: black;
}
.technical ul li:nth-child(2) p:nth-child(2) {
    position: absolute;
    font-size: 14px;
    top: 39px;
}
/* 机械制图 */
.machine-drawing {
    position: relative;
    padding-top: 35px;
}
.machine-drawing ul li:nth-child(2) {
    position: absolute;
    top: 35px;
    left: 120px;
}
.machine-drawing ul li:nth-child(2) p:nth-child(1) {
    font-size: 19px;
    font-weight: 700;
    color: black;
}
.machine-drawing ul li:nth-child(2) p:nth-child(2) {
    position: absolute;
    font-size: 14px;
    top: 39px;
}